1 files changed, 177 insertions, 0 deletions
diff --git a/src/com/p4square/restlet/oauth/OAuthAuthenticatorHelper.java b/src/com/p4square/restlet/oauth/OAuthAuthenticatorHelper.java
new file mode 100644
index 0000000..76ff044
--- /dev/null
+++ b/src/com/p4square/restlet/oauth/OAuthAuthenticatorHelper.java
@@ -0,0 +1,177 @@
+/*
+ * Copyright 2013 Jesse Morgan
+ */
+
+package com.p4square.restlet.oauth;
+
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+
+import java.net.URLEncoder;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+
+import java.util.Collections;
+import java.util.Random;
+
+import javax.crypto.Mac;
+import javax.crypto.SecretKey;
+import javax.crypto.spec.SecretKeySpec;
+
+import org.restlet.Request;
+import org.restlet.Response;
+import org.restlet.data.ChallengeRequest;
+import org.restlet.data.ChallengeResponse;
+import org.restlet.data.ChallengeScheme;
+import org.restlet.data.CharacterSet;
+import org.restlet.data.Form;
+import org.restlet.data.Method;
+import org.restlet.data.Parameter;
+import org.restlet.data.Reference;
+import org.restlet.engine.header.ChallengeWriter;
+import org.restlet.engine.header.Header;
+import org.restlet.engine.security.AuthenticatorHelper;
+import org.restlet.engine.util.Base64;
+import org.restlet.util.Series;
+
+/**
+ * Authentication helper for signing OAuth Requests.
+ *
+ * This implementation is limited to one consumer token/secret per restlet
+ * engine. In practice this means you will only be able to interact with one
+ * service provider unless you loaded/unloaded the AuthenticationHelper for
+ * each request.
+ *
+ * @author Jesse Morgan <jesse@jesterpm.net>
+ */
+public class OAuthAuthenticatorHelper extends AuthenticatorHelper {
+    private static final String SIGNATURE_METHOD = "HMAC-SHA1";
+    private static final String JAVA_SIGNATURE_METHOD = "HmacSHA1";
+    private static final String ENCODING = "UTF-8";
+
+    private final Random mRandom;
+    private final Token mConsumerToken;
+
+    /**
+     * Package-private constructor.
+     *
+     * This class should only be instantiated by OAuthHelper.
+     */
+    OAuthAuthenticatorHelper(Token consumerToken) {
+        super(ChallengeScheme.HTTP_OAUTH, true, false);
+
+        mRandom = new Random();
+        mConsumerToken = consumerToken;
+    }
+
+    @Override
+    public void formatRequest(ChallengeWriter cw, ChallengeRequest cr,
+            Response response, Series<Header> httpHeaders) throws IOException {
+
+        throw new UnsupportedOperationException("OAuth Requests are not implemented");
+    }
+
+    @Override
+    public void formatResponse(ChallengeWriter cw, ChallengeResponse response,
+            Request request, Series<Header> httpHeaders) {
+
+        try {
+            Series<Parameter> authParams = new Series<Parameter>(Parameter.class);
+
+            String nonce = String.valueOf(mRandom.nextInt());
+            String timestamp = String.valueOf(System.currentTimeMillis() / 1000);
+
+            authParams.add(new Parameter("oauth_consumer_key", mConsumerToken.getToken()));
+            authParams.add(new Parameter("oauth_nonce", nonce));
+            authParams.add(new Parameter("oauth_signature_method", SIGNATURE_METHOD));
+            authParams.add(new Parameter("oauth_timestamp", timestamp));
+            authParams.add(new Parameter("oauth_version", "1.0"));
+
+            String accessToken = response.getIdentifier();
+            if (accessToken != null) {
+                authParams.add(new Parameter("oauth_token", accessToken));
+            }
+
+            // Generate Signature
+            String signature = generateSignature(response, request, authParams);
+            authParams.add(new Parameter("oauth_signature", signature));
+
+            // Write Header
+            for (Parameter p : authParams) {
+                cw.appendQuotedChallengeParameter(encode(p.getName()), encode(p.getValue()));
+            }
+
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+
+        } catch (InvalidKeyException e) {
+            throw new RuntimeException(e);
+
+        } catch (NoSuchAlgorithmException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * Helper method to generate an OAuth Signature.
+     */
+    private String generateSignature(ChallengeResponse response, Request request,
+           Series<Parameter> authParams)
+        throws NoSuchAlgorithmException, InvalidKeyException, IOException,
+                          UnsupportedEncodingException {
+
+        // HTTP Request Method
+        String httpMethod = request.getMethod().getName();
+
+        // Request Url
+        Reference url = request.getResourceRef();
+        String requestUrl = encode(url.getScheme() + ":" + url.getHierarchicalPart());
+
+        // Normalized parameters
+        Series<Parameter> params = new Series<Parameter>(Parameter.class);
+
+        // OAUTH Params
+        params.addAll(authParams);
+
+        // Query Params
+        Form query = url.getQueryAsForm();
+        params.addAll(query);
+
+        // Sort it
+        Collections.sort(params);
+
+        StringBuilder normalizedParamsBuilder = new StringBuilder();
+        for (Parameter p : params) {
+            normalizedParamsBuilder.append('&');
+            normalizedParamsBuilder.append(p.encode(CharacterSet.UTF_8));
+        }
+        String normalizedParams = encode(normalizedParamsBuilder.substring(1)); // remove the first &
+
+        // Generate signature base
+        String sigBase = httpMethod + "&" + requestUrl + "&" + normalizedParams.toString();
+
+        // Sign the signature base
+        Mac mac = Mac.getInstance(JAVA_SIGNATURE_METHOD);
+
+        String accessTokenSecret = "";
+        if (response.getIdentifier() != null) {
+            accessTokenSecret = new String(response.getSecret());
+        }
+
+        byte[] keyBytes = (encode(mConsumerToken.getSecret()) + "&" + encode(accessTokenSecret)).getBytes(ENCODING);
+        SecretKey key = new SecretKeySpec(keyBytes, JAVA_SIGNATURE_METHOD);
+        mac.init(key);
+
+        byte[] signature = mac.doFinal(sigBase.getBytes(ENCODING));
+
+        return Base64.encode(signature, false).trim();
+    }
+
+    /**
+     * Helper method to URL Encode Strings.
+     */
+    private String encode(String input) throws UnsupportedEncodingException {
+        return URLEncoder.encode(input, ENCODING);
+    }
+}